The Dissociation Constant in Nitrogen Fixation by Azotobacter

6 Dodge originally used "A" and "a" to designate the two sex types in Neurospora crassa. Lindegren later substituted the symbols "+" and "-" for these. Because of the desirability of using the symbol + for the normal allele of a gene and also to designate a positive experimental result, we prefer Dodge's original designations. 4 Neither conversion of pimelic acid to p-aminobenzoic acid by the normal strain nor anti-sulfanilamide activity of pimelic acid could be detected. 7 See Woods, D., and Fildes, P., Chem. Ind., 59, 133 (1940); Woods, D., Brit. Jour. Exp. Path., 21, 74 (1940); and Landy, M., and Wyeno, J., Proc. Soc. Exp. Biol. Med., 46, 59 (1941). 8 Wiedling, S., Science, 94, 389 (1941). 9 Dimond, N. S., Ibid., 94, 420 (1941). 10 See Beadle, G. W., and Tatum, E. L., Amer. Nat., 75, 107 (1941), and loc. cit., footnote 3. 11 All the compounds tested were carefully purified to remove any possible traces of paminobenzoic acid. The aniline was prepared by hydrolysis of recrystallized acetanilide and subsequent distillation. 12 A bacteriostatic action of p-nitrobenzoic acid has been reported. See King, J. T., and Henschel, A. F., Proc. Soc. Exp. Biol. Med., 47, 400 (1941). 1" The other active compounds were toxic in concentrations theoretically high enough to overcome the sulfanilamide inhibition.